View Full Version : Red pixel on an image - hot pixel, right?
Matholwch
20-09-2005, 10:35
Noticed recently that I might well have a hot pixel on my new 20D. Not particularly impressed by this, since some of the exposures I've taken weren't very long.
What can I do? Bought from Jessops, any comeback with this - can I take it back and ask for a replacement?
I doubt it. If it's a single pixel, I'd live with it. I take it you're shooting RAW? Convert to jpg and it'll disappear. Also, the simplest thing to fix in any photo editor.
Matholwch
20-09-2005, 10:50
Wasn't shot in RAW, its a small cluster of pixels :(
http://www.rhif12.co.uk/album/data/7/1IMG_6995_1.jpg
Blimey, if that's the full frame, it's one hell of a spot. (if it's not, how much of a crop is it?) I'd take it back and show them, see what they say then start kicking up a fuss.
EDIT: Actually, looking at the resolution, it seems quite a small part of the frame.
Matholwch
20-09-2005, 11:13
It is a crop of this image
http://www.rhif12.co.uk/rhif12/Wales/slides/IMG_6995_1.jpg
click for full version. (http://www.rhif12.co.uk/rhif12/Wales/IMG_6995_1.jpg)
But its quite clearly more than the one pixel, and its not even a very long exposure.
sideshowbob
20-09-2005, 11:35
You sure it isn't something else? have you tried a long exposure with the cap on?
Matholwch
20-09-2005, 11:55
Haven't tried that yet, but I've spotted it on another photo of mine this morning. Currently updating the site to remove family photos.
puddleduck
20-09-2005, 13:33
My 3rd (or was it 4th, I lose count!) D70 had some hot red pixels and Jessops swapped it over no problem - I'd give it a go, they look pretty bad to me.
They swapped mine when I took it back for having a dusty sensor ;) :suspect:
sideshowbob
20-09-2005, 15:08
:lol: That's outrageous.
Matholwch
20-09-2005, 15:23
Just rang them up, and they asked me to bring it in for them to have a look and see what they can do about replacing it, although they also said it was borderline send it back for repairs... Now the next thing I wonder is if they do exchange it, will I be able to claim the £100 cashback from Canon ;)
phillied
20-09-2005, 15:26
Haven't tried that yet, but I've spotted it on another photo of mine this morning. Currently updating the site to remove family photos.
I've sent my 10D back for the same problem. Was really disappointed when I saw it! It's the same on other images I've taken.
It was still under warranty so it's gone back to Canon for fixing. Not had it back yet - likely to be most of a month :(
I certainly wouldn't be happy living with it - I know I'd miss cloning it on some images, and I'd regret it when I printed at A4!!
Phil
From what I can tell nearly all digital cameras suffer from them to some extent unless the owner is incredibly lucky. They're most noticable in the Canons DSLR line since they don't do automatic dark frame subtraction for long exposures by default. I think on the 20D canon will map out the pixels in the firmware (though maybe not for a cluster that size).
Also they develop with use, but you shouldn't have a cluster that big on a new sensor.
Matholwch
21-09-2005, 14:49
Last night I tried to recreate the hot pixel, only appreared after I'd taken about 6 or so long exposure shots with the lens cap over it. But I'm guessing it stays hot for a while, because with that photo I posted, there had been a 10 min interval from a couple of long exposures of the river and then taking a photo of the cricketers.
:dork: Charge trapping - there is a strain in the silicon latice that can trap electrons ( or actually holes - absence of electrons ) once you get a charge in there from a very high signal level or a long exposure it stays there, even without power on the CCD.
There are things the CCD driver can do in the clocking to shift it - don't know what SLRs do compared to astronomy CCD cameras - interestingly the same thing can be used in archeology, electrons trapped in ceramic glaze when a pot is fired can stay there for 1000s of years !
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